Remove tab layout feature flag and unused code

.storybook/Container.scss

@@ -1,5 +1,5 @@
 /*
-Copyright 2019-2024 The Tekton Authors
+Copyright 2019-2026 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -28,3 +28,9 @@ limitations under the License.
     background-color: inherit !important;
   }
 }
+
+[role="main"] > .tkn--task-logs {
+  .cds--accordion__heading {
+    inset-block-start: 0; // demonstrate the sticky header behaviour when displayed in isolation
+  }
+}

packages/components/src/components/TaskTree/_TaskTree.scss → packages/components/src/components/AccordionItem/AccordionItem.jsx

@@ -1,5 +1,5 @@
 /*
-Copyright 2019-2024 The Tekton Authors
+Copyright 2025-2026 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -11,7 +11,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-.tkn--task-tree {
-  inline-size: 21%;
-  min-inline-size: 15rem;
+import { AccordionItem as CarbonAccordionItem } from '@carbon/react';
+
+function AccordionItem({ children, open, ...rest }) {
+  return (
+    <CarbonAccordionItem open={open} {...rest}>
+      {open ? children : null}
+    </CarbonAccordionItem>
+  );
 }
+
+export default AccordionItem;

packages/components/src/components/AccordionItem/AccordionItem.stories.jsx

@@ -0,0 +1,75 @@
+/*
+Copyright 2026 The Tekton Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Accordion } from '@carbon/react';
+
+import AccordionItem from './AccordionItem';
+
+export default {
+  component: AccordionItem,
+  title: 'AccordionItem'
+};
+
+export const Closed = {
+  args: {
+    open: false,
+    title: 'Closed Accordion Item',
+    children: <div>This content is not rendered when closed</div>
+  },
+  decorators: [
+    Story => (
+      <Accordion>
+        <Story />
+      </Accordion>
+    )
+  ]
+};
+
+export const Open = {
+  args: {
+    open: true,
+    title: 'Open Accordion Item',
+    children: (
+      <div>
+        <p>This content is rendered when open</p>
+        <p>
+          The AccordionItem optimizes rendering by only rendering children when
+          open
+        </p>
+      </div>
+    )
+  },
+  decorators: [
+    Story => (
+      <Accordion>
+        <Story />
+      </Accordion>
+    )
+  ]
+};
+
+export const MultipleItems = {
+  render: () => (
+    <Accordion>
+      <AccordionItem open title="First Item">
+        <p>Content of first item</p>
+      </AccordionItem>
+      <AccordionItem open={false} title="Second Item">
+        <p>Content of second item (not rendered)</p>
+      </AccordionItem>
+      <AccordionItem open title="Third Item">
+        <p>Content of third item</p>
+      </AccordionItem>
+    </Accordion>
+  )
+};

packages/components/src/components/AccordionItem/AccordionItem.test.jsx

@@ -0,0 +1,51 @@
+/*
+Copyright 2026 The Tekton Authors
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { render } from '../../utils/test';
+
+import AccordionItem from './AccordionItem';
+
+describe('AccordionItem', () => {
+  it('should render children when open is true', () => {
+    const { queryByText } = render(
+      <AccordionItem open title="Test Title">
+        <div>Test Content</div>
+      </AccordionItem>
+    );
+    expect(queryByText('Test Content')).toBeTruthy();
+  });
+
+  it('should not render children when open is false', () => {
+    const { queryByText } = render(
+      <AccordionItem open={false} title="Test Title">
+        <div>Test Content</div>
+      </AccordionItem>
+    );
+    expect(queryByText('Test Content')).toBeFalsy();
+  });
+
+  it('should pass through other props to CarbonAccordionItem', () => {
+    const { container } = render(
+      <AccordionItem
+        open
+        title="Test Title"
+        className="custom-class"
+        data-testid="test-accordion"
+      >
+        <div>Test Content</div>
+      </AccordionItem>
+    );
+    const accordionItem = container.querySelector('.custom-class');
+    expect(accordionItem).toBeTruthy();
+  });
+});

packages/components/src/components/TaskTree/index.js → packages/components/src/components/AccordionItem/index.js

@@ -1,5 +1,5 @@
 /*
-Copyright 2019-2021 The Tekton Authors
+Copyright 2026 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -12,4 +12,4 @@ limitations under the License.
 */
 /* istanbul ignore file */
 
-export { default } from './TaskTree';
+export { default } from './AccordionItem';

packages/components/src/components/DetailsHeader/_DetailsHeader.scss

@@ -42,12 +42,6 @@ header.tkn--step-details-header {
     .#{$prefix}--btn-set {
       margin-inline: 0.5rem;
       align-self: center;
-      align-items: baseline;
-
-      .cds--btn--icon-only {
-        inline-size: 2rem;
-        block-size: 2rem;
-      }
     }
 
     .tkn--run-details-name {

packages/components/src/components/Log/_Log.scss

@@ -1,5 +1,5 @@
 /*
-Copyright 2019-2025 The Tekton Authors
+Copyright 2019-2026 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -72,37 +72,7 @@ pre.tkn--log {
   .#{$prefix}--btn-set {
     position: absolute;
     inset-block-start: 0;
-    inset-inline-end: var(--tkn-log-inline-padding);
-    align-items: center;
-  }
-
-  .button-container {
-    position: absolute;
-    clip-path: inset(0); // ensure the children with position:fixed are not shown outside this element.
-    inset-block-start: 3.125rem; //equals the maximum between padding-block-start of pre.tkn--log and between the page header height
-    inset-block-end: 0;
-    inset-inline-end: 0;
-    inline-size: var(--tkn-log-inline-padding);
-  }
-
-  .#{$prefix}--btn--ghost,
-  .#{$prefix}--copy-btn {
-    inline-size: 2rem;
-    block-size: 2rem;
-    min-block-size: 2rem;
-    background-color: $background;
-
-    &:hover {
-      background-color: $layer-hover;
-    }
-
-    &:focus {
-      outline-color: white;
-    }
-
-    svg {
-      fill: $icon-primary;
-    }
+    inset-inline-end: 0.5rem; // var(--tkn-log-inline-padding);
   }
 
   .tkn--log-trailer {